1- alkynylphosphines, hydrothiolation

Hydrothiolation of 1-alkynylphosphines was catalyzed by P(OAc)2 in EtOH and gave Z-l-phosphino-2-thio-l-alkene as product (Scheme 3.87) [156]. Surprisingly, the addition reaction took place in the anti-fashion, which probably means an external nucleophilic attack on the coordinated triple bond as a key-step instead of the alkyne insertion observed in the other examples. 

While terminal alkynes are typically used for metal-catalyzed hydrothiolation reactions, the treatment of 1-alkynylphosphines 18 with a variety of thiols in the presence of Pd(OAc)2 resulted in (Z)-isomers 19 through a preferential coordination of the substrate phosphine to a Pd metal center 20 followed by nucleophilic attack of thiol and protonolysis.In 2010, Liu and co-workers reported on the Cu-catalyzed decarboxylative cross-coupling of arylpropiolic acids 21 with thiols for the synthesis of vinyl sulfides 22 with high stereoselectivity for (Z)-isomers. ... 

Kondoh A, Yorimitsu H, Oshima K. Palladium-catalyzed a ri-hydrothiolation of 1-alkynylphosphines. Org. Lett. 2007 9 1383-1385. 

The Pd(OAc)2-catalyzed hydrothiolation of 1-alkynylphosphines 7 was reported in 2007 [26]. This reaction yields (Z)-l-phosphino-2-thio-l-alkenes 8 regio- and stereoselectively in anfi-hydrothiolation fashion (6). From the stereochemistry observed, the following mechanism was proposed, where Pd(II) coordinates on the phosphorus atom to induce the addition of RSH (Scheme 8). 

Scheme 8 Catalytic cycle for Pd(OAc)2-catalyzed hydrothiolation of l-alkynylphosphines...

Palladium-catalyzed hydrothiolation of alkynylphosphines proceeds via anti-addition process, yielding the corresponding (Z)-l-phosphino-2-thioalkenes regio-and stereoselectively. The coordination of the phosphino group to the palladium induces the rare example of catalytic anti-addition of thiols to alkynes (Scheme 30)... 

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